References:  local anaesthesia and TAC vs. LET

Schilling CG, Bank DE, Borchert BA, Klatzko MD, Uden DL 
Tetracaine, epinephrine (adrenalin), and cocaine (TAC) versus
lidocaine, epinephrine, and tetracaine (LET) for anesthesia of lacerations
in children.  
Ann Emerg Med 1995 Feb;25(2):203-8 

ABSTRACT:  STUDY
OBJECTIVE: To compare the duration of anesthesia experienced with
lidocaine, epinephrine, and tetracaine (LET) solution and that with
tetracaine, epinephrine (Adrenalin), and cocaine (TAC) solution during
suturing of uncomplicated lacerations on the face or scalp. DESIGN: 
Double-blind, randomized, controlled trial. SETTING: The emergency
department of a university-affiliated private children's hospital. 
PARTICIPANTS: One hundred seventy-one children with lacerations on the
face and scalp requiring suturing. INTERVENTIONS: After standard
application of the anesthetic solution, patients were assessed for signs
of discomfort before and during laceration repair. Duration of anesthesia
during laceration repair was determined on the basis of the length of time
after removal of the anesthetic solution to the first sign(s) of
discomfort that required additional anesthesia. RESULTS: There was no
statistical difference between TAC and LET in adequacy of anesthesia
before suturing or in duration of anesthesia during suturing. CONCLUSION:
LET is an effective alternative to TAC for topical anesthesia during
suturing of uncomplicated lacerations on the face and scalp in children. 

Blackburn PA, Butler KH, Hughes MJ, Clark MR, Riker RL 
Comparison of tetracaine-adrenaline-cocaine (TAC) with topical 
lidocaine-epinephrine (TLE): efficacy and cost.  
Am J Emerg Med 1995 May;13(3):315-7 
ABSTRACT: 

Topical anesthesia in the form of TAC (tetracaine, adrenaline, cocaine)
solution has been used for wound repair. This pilot study was designed to
determine if the topical anesthesia achieved using a mixture of lidocaine
(5%) and epinephrine (1:2000) (TLE) is equivalent to the topical
anesthesia obtained using a solution of tetracaine (0.5%), epinephrine (1:
2000), and cocaine (10.4%) (TAC). A prospective, randomized, double-blind
trial was carried out from May 1992 to August 1992 at a community-based
teaching hospital Emergency Department (ED) that receives 50,000 annual
visits.  Patients with facial or scalp lacerations suitable for topical
anesthesia presenting to the ED were included when study physicians were
in attendance.  Exclusion criteria included the presence of a sensory
altering substance (eg, ethanol), age younger than two years,
hypertension, pregnancy, allergy to any of the study's pharmacological
agents, wounds greater than six hours old, grossly contaminated wounds,
and wounds longer than six centimeters.  Either a TAC or TLE solution was
applied to lacerations before suturing. The laceration was repaired and
the patient or physician evaluated the degree of pain from the procedure
by using a standardized visual pain scale. A total of 35 patients were
studied. Seventeen patients were in the TLE group; 18 in the TAC group.
The mean ages were compared and found to be similar (P = .40) between the
two test groups. The pain scale values, the diameter of tissue blanch
around laceration (halo size), and the time to laceration repair from the
onset of application of anesthetic were compared and no difference was
shown between the TAC and TLE groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Ernst AA, Marvez-Valls E, Nick TG, Weiss SJ 
LAT (lidocaine-adrenaline-tetracaine) versus TAC
(tetracaine-adrenaline-cocaine) for topical anesthesia in face and scalp
lacerations.  
Am J Emerg Med 1995 Mar;13(2):151-4 

ABSTRACT:  
The study objective was to compare the topical anesthetic LAT (4% lidocaine, 
1:2,000 adrenaline, 1% tetracaine) to TAC (0.5% tetracaine, 1:2,000 
adrenaline, 11.8% cocaine) for efficacy, adverse effects, and costs. The 
study design was a randomized, prospective, double blind clinical trial 
set in an inner-city emergency department with an emergency medicine 
residency
program. Adults with linear lacerations of the face or scalp were eligible
for inclusion in the study. Patients had lacerations anesthetized with
topical TAC or LAT according to a random numbers table. A total of 95
patients were included in the study with 47 receiving TAC and 48 receiving
LAT. Patients stated the number of sutures causing pain and patients and
physicians rated the overall pain of suturing using a standard visual
analog scale (VAS). The power of the study to determine a ranked sum
difference of 15 was 0.8. Visual analog scale results and number and
percentage of sutures causing pain were compared using Wilcoxon's Rank Sum
Test. According to patients, the percentage of sutures causing pain was
significantly fewer for LAT than TAC (P = .036, Interquartile Range 0.13
to 0.0 for LAT, 0.25 to 0 for TAC). Physicians found LAT statistically
more effective than TAC (P = .0093, Interquartile Range 1 to 0 for LAT, 2
to 0 for TAC) but patients did not report a difference (P = .266,
Interquartile Range 1 to 0 for both LAT and TAC). Our cost per application
was $3.00 for LAT compared to $35.00 for TAC. Follow-up was accomplished
in 91 of 95 patients (95%) with no reported complications for either
medication.(ABSTRACT TRUNCATED AT 250 WORDS

Ernst AA, Marvez E, Nick TG, Chin E, Wood E, Gonzaba WT 
Lidocaine adrenaline tetracaine gel versus tetracaine adrenaline cocaine 
gel for topical anesthesia in linear scalp and facial lacerations in 
children aged 5 to 17 years.  
Pediatrics 1995 Feb;95(2):255-8 

ABSTRACT:  STUDY OBJECTIVE. 
The purpose of the present study is to compare LAT gel (4%
lidocaine, 1:2000 adrenaline, 0.5% tetracaine) to TAC gel (0.5%
tetracaine, 1:2000 adrenaline, 11.8% cocaine) for efficacy, side effects,
and costs in children aged 5 to 17 years with facial or scalp lacerations.
DESIGN.  Randomized, prospective, double-blinded clinical trial. SETTING.
Inner-city Emergency Department with an Emergency Medicine residency
program. PATIENTS OR OTHER PARTICIPANTS. Children aged 5 to 17 years with
linear lacerations of the face or scalp. INTERVENTION. After informed
consent was obtained patients had lacerations anesthetized with topical
TAC or LAT gel according to a random numbers table. MEASUREMENTS AND MAIN
RESULTS. A total of 95 patients were included in the statistical analysis
with 47 receiving TAC and 48 receiving LAT. Physicians and
patients/parents separately rated the overall pain of suturing using a
modified multidimensional scale for pain assessment specifically for
children. Patients/parents also stated the number of sutures causing pain.
The power of the study to determine a ranked sum difference of 15 was 0.8.
Multidimensional rating scale results and number and percentage of sutures
causing pain were compared using Wilcoxon's rank sum test. According to
patients no difference could be detected in percent of sutures causing
pain in the LAT versus TAC group (P = .51). Using the multidimensional
scale, physicians and patients/parents found LAT statistically the same as
TAC in effectiveness (P = .80 for physicians and P = .71 for patients).
Cost per application was $3.00 for LAT compared to $35.00 for TAC.
Follow-up was accomplished in 85 of 95 participants in the study with no
reported complications for either medication. CONCLUSION. LAT gel worked
as well as TAC gel for topical anesthesia in facial and scalp lacerations.
Considering the advantages of a noncontrolled substance and less expense,
LAT gel appears to be better suited than TAC gel for topical
anesthesia in laceration repair in children. 

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References:  Warming and Buffering Local Anaesthetics
=====================================================

DOES WARMING LOCAL ANESTHETIC REDUCE THE PAIN OF SUBCUTANEOUS INJECTION?
Martin, S., et al, Am J Emerg Med 14(1):10, January 1996
BACKGROUND: Techniques that have been suggested to reduce the pain of
local infiltration of amide anesthetics include alkalinization of the
solution with sodium bicarbonate, avoidance of epinephrine combinations,
use of small gauge needles, and slow injection. Warming of the solution
to body temperature has also been advocated, but has not been
consistently shown to ameliorate the pain of anesthetic injection.
METHODS: This randomized, prospective, crossover study, from Butterworth
Hospital and Michigan State University College of Human Medicine in
Grand Rapids, examined the effect of warming on the pain of injection of
buffered 1% lidocaine in 40 adult volunteers. Each participant underwent
subcutaneous injection of 1ml aliquots of both room temperature (20C)
and warmed "body temperature" (37C) 1% lidocaine buffered with
bicarbonate, and assessed the pain of actual lidocaine injection on a
100mm visual analogue scale. 
RESULTS: Room temperature lidocaine injection was considered to be the
more painful of the two solutions by 50% of the participants, while body
temperature lidocaine was considered the more painful by 43% (7%
perceived no difference). The pain of the initial needle stick was
assigned a VAS score of 5mm. Median pain scores for injection of 20C and
37C buffered lidocaine solutions were 40mm and 35mm, respectively.
CONCLUSIONS: Warming of buffered lidocaine to body temperature does not
appear to significantly ameliorate the pain of subcutaneous injection.

Murakami CS, Odland PB, Ross BK
Buffered local anesthetics and epinephrine degradation.
J Dermatol Surg Oncol 1994 Mar;20(3):192-5
Lidocaine with epinephrine is currently the most common local anesthetic
agent used for facial soft tissue surgery. This combination is generally
safe and effective in providing complete anesthesia and adequate hemostasis.
Because epinephrine is unstable at physiologic pH, the commercial
preparation is formulated with a low pH (3.5-5.5). Unfortunately, this
acidic pH causes significant pain during infiltration. To reduce pain,
clinicians sometimes buffer acidic local anesthetic agents with sodium
bicarbonate. However, little is known about the stability of epinephrine
when the pH of epinephrine is clinically altered. Using high pressure liquid
chromatography (HPLC), epinephrine levels were measured after the addition
of sodium bicarbonate. Our results indicate a significant amount of
epinephrine degradation occurs in some of these specimens. Recommendations
regarding the use of buffered local anesthetic agents are made.

Bartfield, Acad. EM, 2(4):254, April 1995
1.  38.9C unbuffered lido v. RT (?C) 1:10 buffered lido, n=10
2.  Warmed buffered v. RT buffered, n=24
Outcome measured on 100 mm visual analog score.
All volunteers, no trauma.
Results:
Group 1:
Median pain score: 38.9C = 46, RT buffered = 13, 9/10 subjects preferred
buffered. Group 2: Median pain scores of 15 and 16, respectively. Analysis:
RT and buffered give same pain score, warm plain different. Thus, buffering
appears to make the difference.

Brogan, Annals of EM, 26(2):121, August 1995
n=40
age > 13
3 arms: warmed (37C), buffered RT, plain RT.
All were patients, all suffered trauma.
One side of the wound injected with warmed, the other buffered (n=18). 3
groups of 9 each had one type only for both wound margins. Visual analog
scale used. Buffered: 4.7 Warmed plain: 4.9 Plain RT: 8.2 Additional
anesthesia needed: Warmed: 0/9 Buffered: 1/9 Plain RT: 3/9 Analysis:
Inadequate anesthesia training or use by the practitioners. (There is no
logical reason that 1/3 of patients receiving 22 -25C lidocaine wouldn't
warm it to 37C themselves.)

Martin, Am. Journ. of EM, 14(1):10, Jan. 1996
n=40
Volunteers, no trauma.
1:10 lido, 20C and 37C.
100 mm visual analog scale.
1 cc injection.
Results:
Needle stick: 5 mm (assigned)
20C more painful: 50%
37C more painful: 43%
No difference: 7%
20C: 40 mm
37C: 35 mm
Analysis: Warming makes no difference to pain from buffered lido.

Hardy SJ, Agostini DE
Accidental epinephrine auto-injector-induced digital ischemia reversed by
phentolamine digital block.
J Am Osteopath Assoc 1995 Jun;95(6):377-8

The use of epinephrine-containing auto-injectors as a prescription
medication for treating routine to severe anaphylactic reactions is now
widely accepted. Associated with this trend is an increasing number of
accidental injections of epinephrine into digits, causing severe
vasoconstriction and the risk of ischemic necrosis. When epinephrine is
accidentally discharged into a digit, ischemic skin necrosis resulting
from the alpha-adrenergic blocking effects of this agent can lead to the
need for multiple operations, wound infection, and even loss of the digit.
The alpha-adrenergic blocking characteristics of phentolamine administered
by a variety of methods have proved effective in reversing the effects of
epinephrine in these cases. The authors urge that the described treatment
protocol become more widely disseminated among primary care and emergency
physicians.

Cheney PR, Molzen G, Tandberg D
The effect of pH buffering on reducing the pain associated with
subcutaneous infiltration of bupivicaine [published erratum appears in Am
J Emerg Med 1991 Jul;9(4):410] [see comments]
Am J Emerg Med 1991 Mar;9(2):147-8

The authors propose that pH buffering of bupivicaine with sodium bicarbonate
reduces the pain associated with its local subcutaneous infiltration. In a
double-blind, prospective study, 62 healthy adult volunteers received a 0.5
mL subcutaneous infiltration of 0.5% buffered bupivicaine into the dorsum of
a randomly chosen hand. The pH was adjusted to 7.0 by adding 0.05 mL of
sodium bicarbonate (1 mEq/L [corrected]) to 10 mL vials of commercially
available bupivicaine (1:200 dilution). The control hand was injected with
the same amount of unbuffered agent. Pain was scored after each infiltration
using a nonsegmented visual analogue scale. Student's t-test for paired
measurements was used to analyze intergroup pain score differences.
Forty-three subjects (69%) reported less pain with buffered bupivicaine and
only 17 (27%) noted a modest increase: two subjects (3%) reported no
difference. The mean pain score for the buffered agent was 22 mm compared
with 30 mm for the control. The mean difference (control-experimental) was 8
mm (t = 4.64, df = 61, P less than .001). The authors conclude that the
addition of sodium bicarbonate to bupivicaine reduces the pain associated
with its local infiltration.

Knoop K, Trott A, Syverud S. Comparison of digital versus
metacarpal blocks for repair of finger injuries. Ann Emerg Med.
1994;23:1296-300.]

STUDY OBJECTIVE: This study compared efficacy, degree of discomfort,
and time to anesthesia of digital blocks and metacarpal blocks for
digital anesthesia. DESIGN: Randomized, prospective, nonblinded,
clinical study conducted from April 1992 to January 1993. Patients
served as their own controls. SETTING: Inner-city and community
hospital emergency departments. TYPE OF PARTICIPANTS: Convenience
sample of 30 adult patients, with third or fourth finger injuries
including and distal to the proximal interphalangeal joint that
required digital anesthesia. INTERVENTIONS: Digital blocks and a
metacarpal blocks were performed (one per side) on all 30 patients
(total of 60 blocks). The order of the blocks was randomized.
MEASUREMENTS: A digital block and a metacarpal block were performed
on each patient. Patients immediately rated the pain associated with
each technique on a nonsegmented visual analog scale. Efficacy was
assessed by requirement for additional anesthesia and anesthesia to
pinprick. Time to anesthesia was assessed after each block in 23
patients. RESULTS: Mean visual analog scale pain scores were 2.53
for digital block and 3.38 for metacarpal block (P = .1751,
Student's t-test). Metacarpal block failed anesthesia to pinprick in
23% of patients compared to 3% for digital block (P = .0227, chi 2).
Time to anesthesia was significantly shorter for digital block
compared to metacarpal block, with a mean of 2.82 minutes versus
6.35 minutes (P < .0001, Student's t-test). CONCLUSION: Digital
block and metacarpal block, as described in this study, are equally
painful procedures. Digital block, however, is more efficacious and
requires significantly less time to anesthesia for the injured
finger.

This small study shows that it works better in the web space than in
the metacarpal head area, and if it were a bigger study I'm sure it
would have shown it to be less painful (based on my own clinical
experience).

[Mader TJ, Playe SJ, Garb JL. Reducing the pain of local anesthetic
infiltration: warming and buffering have a synergistic effect. Ann
Emerg Med. 1994;23:550-4.]

STUDY OBJECTIVE: To compare room-temperature unbuffered lidocaine,
warm lidocaine, buffered lidocaine, and warm buffered lidocaine to
determine which of the four solutions is least painful during
infiltration. DESIGN: Randomized, controlled, double-blinded,
volunteer study. TYPE OF PARTICIPANT: Thirty-two young healthy
adults. MAIN RESULTS: Each subject received four subcutaneous
injections of 1% lidocaine: room-temperature unbuffered, warm,
buffered, and warm buffered. After each injection, participants
recorded their perception of pain associated with infiltration of
the solution on a visual analog scale. Mean pain scores for the four
solutions were determined and analyzed. The mean perceived pain
score for the warm buffered solution was significantly lower than
for any of the other solutions (versus warm: P = .0005; versus
buffered: P = .0028; versus room temperature: P = .0001). There was
no statistically significant difference between either the warm
solution or buffered solution and the room-temperature unbuffered
lidocaine. The difference in mean pain score for the warm buffered
solution, compared with those for the warm, buffered, and
room-temperature solutions, suggests that warming and buffering have
a synergistic effect. CONCLUSION: Skin infiltration with warm
buffered lidocaine is significantly less painful than infiltration
with room-temperature unbuffered lidocaine, warm lidocaine, or
buffered lidocaine.